Transmit AOVs incorrect for custom AOVs in semi-transmissive areas and on empty bg

[sagrothWXF5L]

I want to get RGB masks for objects in refraction (street behind the window or pupil/iris behind cornea) and create custom AOV with solid colors for that. Transmit AOVs option works fine, but fails in two situations:

1) any transmission weight below 1.0 counts as 0 and instead of the smooth gradient I get a hard line;

2) on empty bg custom AOV returns glass values instead of 0.

Here's a simple example - top plane has a transmission weight mapped with a gradient and red ramp in custom AOV... Bottom plane has blue ramp in custom AOV:

That's what I get in custom AOV - gradient is not respected and areas over nothing are red from the top plane:

Here's the scene:

transmitaovs02.zip

In a more practical situation I have a gradient in transmission weight for the cornea edge, but custom AOV is sharp and doesn't match (green-blue edge):

[ashley.handscomb.retallack]

This was already reported, we have made a ticket for this.